1. Field of the Invention
The present invention generally relates to a backlight apparatus, and a liquid crystal display (LCD), and especially relates to a backlight apparatus including a luminescent source that generates heat, such as a fluorescent lamp, and an LCD that employs the backlight apparatus.
Conventionally, CRT (cathode-ray tube) displays have been used. In recent years, use of thin displays that employ an LCD panel has been progressing. Display quality of the LCD has been enhanced, and enlargement and higher brightness of the displays are desired for television use, etc. With requirements of brighter LCDs increasing, demands are increasing for a backlight apparatus that can provide the illumination for the enlarged and brighter liquid crystal panel.
2. Description of the Related Art
Conventional LCDs have been used mainly by notebook PCs, when up to about 13 inch displays are the main thrust with a screen brightness of around 150 cd/m2 and a resolution of XGA. FIG. 1 and FIG. 2 show an LCD 1A that is an example of a conventional LCD.
The LCD 1A is configured with a liquid crystal panel 2A, a housing 5, a backlight apparatus 10A, etc. The housing 5 holds the liquid crystal panel 2A and the backlight apparatus 10A through a resin frame 6 and a backboard 9. Here, the backlight apparatus 10A gives predetermined brightness to a display of the liquid crystal panel 2A by illuminating the liquid crystal panel 2A from the back.
The backlight apparatus 10A generally includes a fluorescent light bulb 3 serving as a light source, a light guide board 4 that guides the light from the fluorescent light bulb 3 to the liquid crystal panel 2A, and a holder 7 that reflects the light from the fluorescent light bulb 3 to the light guide board 4, while supporting the fluorescent light bulb 3 via a rubber holder.
In the fluorescent light bulb 3, mercury is enclosed in Ar gas or Ne gas, and, on the wall of the fluorescent light bulb 3, a fluorescent material is applied. Mercury gas generates ultraviolet rays during electric discharge, and light is generated when the ultraviolet rays hit the fluorescent material.
The light guide board 4, made from acrylic resin, collaborates with an optical sheet 8 installed, and transmits the light from the fluorescent light bulb 3 and distributes the light all over the liquid crystal panel 2A. In the case of the LCD 1A that provides a relatively small screen size (about 13 inches), where no particularly high resolution and no particularly high screen brightness are required, the backlight apparatus 10A is provided only on one side of the light guide board 4, and only one fluorescent light bulb 3 is provided.
A larger screen size, 14 to 15 inches, has been used for the monitor of a desktop PC. FIGS. 3 and 4 show an LCD 1B that provides a relatively large screen size, for which resolution of SXGA and screen brightness of about 250 cd/m are required. For this reason, two backlight apparatuses 10B are installed in the LCD 1B, such that one of the backlight apparatuses is provided on each side of the light guide board 4. Further, each backlight apparatus 10B includes two fluorescent light bulbs 3. However, with infusion of DVD drives, users require that PC monitors provide even larger screens and higher brightness for movie viewing and so on.
In order to increase the screen size and brightness, there is a problem to solve. That is, the fluorescent light bulb 3 provided in the backlight apparatus 10B generates heat with luminescence. Especially in both ends of the fluorescent light bulb 3 where electrodes are installed, temperature can rise higher than 120 degrees C., when a large electric current is provided in order to obtain a high brightness. For this reason, some conventional solutions provide a rubber holder made of a heat-conductive material at both ends of the fluorescent light bulb 3, such that heat can be dissipated to the holder 7.
Nevertheless, the heat generated by the fluorescent light bulb 3 cannot be sufficiently dissipated by the holder 7 via the rubber holder, causing lowering of the brightness of the fluorescent light bulb 3, and breaking of a solder joint that connects the electrode section and wiring. Another solution has been to provide a larger holder 7 for more efficient heat dissipation, however, it causes dimensions of the LCDs 1A and 1B to become large.
The present invention is made in view of the above-mentioned point, and it aims at offering a backlight apparatus that can efficiently dissipate the heat generated in the luminescent source, and an LCD that employs the backlight apparatus.